Apparatus for the evaporation of active ingredients such as, for example, pyrethrum, incorporated in cellulose or other carrier materials

ABSTRACT

An apparatus for the evaporation of active ingredients incorporated in cellulose or some other, at least approximately dimensionally stable carrier material has heating means arranged in a housing to evaporate the active ingredients. A support is provided for replaceably holding an active ingredient carrier above the heating means. The active ingredient carrier is in the form of a column and is optionally inserted replaceably, with its longitudinal dimension placed vertically, in a sleeve which is adapted in its form and dimensions to the active ingredient carrier and is open at the top and bottom. The sleeve is situated inside the housing and spaced apart from the wall of the housing on all sides, said housing having exhaust gas openings at the top.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to devices for the evaporation of activeingredients incorporated in a carrier.

2. Description of the Prior Art

In the known apparatus German Auslegeschrift No. 2,730,855, the activeingredient carrier in the form of a plate and for the purpose ofevaporation of the active ingredients it is placed with its wholesurface against the electric heating means which are situated behind awindow in the housing and are heated to the operating temperature.

Intense evaporation of active ingredients can be achieved by thisarrangement but the more intense the rate of evaporation the sooner willthe reserve of active ingredients in the active ingredient plate beexhausted, with the result that the plate must be replaced after arelatively short time if a constant rate of evaporation of activeingredient over a considerable period is required.

SUMMARY OF THE INVENTION

It is an object of the present invention to improve an apparatus of thetype indicated so that correctly dosed evaporation of active ingredientsas required for the given circumstances can be achieved by simple meansand over a much longer period of time than with known apparatus withoutthe need to replace the active ingredient carrier.

The solution to this problem is characterised in that the activeingredient carrier is in the form of a column and optionally is insertedreplaceably, with its longitudinal dimension vertically, in a sleevewhich is adapted to the active ingredient carrier in its form anddimensions and is open at the top and bottom, and in that optionally thesleeve is arranged inside the housing so as to be spaced apart from thehousing wall on all sides, which housing has exhaust gas openings onlyat the top.

Due to these measures, the surface area of active ingredient carrierfacing the electric heating means and therefore exposed to the heatingfor evaporation of the active ingredients is relatively small comparedwith the volume of active ingredient carrier.

This not only ensures a well controlled rate of evaporation of activeingredients but also enables the capacity of the active ingredientcarrier to be increased without any increase in the surface area ofactive ingredient carrier exposed to the action of the heating means.

Furthermore, the stream of air which flows upwards through the exhaustgas duct bounded by the sleeve and the wall of the housing and which hasalso been heated by the heating means absorbs the evaporated activeingredients by suction and carries them along at relatively high speedso that the evaporated active ingredients are uniformly distributed inthe surrounding atmosphere at an hitherto unobtainable speed.

It is advantageous if the sleeve and the active ingredient carrier aresituated at a vertical distance from the heating means, inter alia inorder that less heat resistant and therefore less expensive materialsmay be used for the sleeve.

One advantageous further development of the apparatus described aboveconsists in that the distance of the sleeve with active ingredientcarrier from the heating means is adjustable.

This enables the intensity of evaporation to be altered by altering thedistance of the sleeve with active ingredient carrier from the heatingmeans, for example so that a constant rate of evaporation of activeingredient can be maintained over a prolonged period of operation.

Furthermore, for increasing the exchange of heat by convection, it isadvantageous to arrange the sleeve with active ingredient carriercentrally above the heating means and to ensure that the radiant area ofthe heating means is greater than the area of the end face of activeingredient carrier exposed to the heating means.

One variation for selectively altering the degree of evaporation ofactive ingredient is characterised by electric heating means having anadjustable operating temperature.

An embodiment of the invention is described below by way of example withreference to the drawings, in which

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents a section taken on line I--I of FIG. 2 through anapparatus for the evaporation of active ingredients incorporated incellulose or other carrier materials;

FIG. 2 represents the same apparatus viewed from above;

FIG. 3 represents the same in side view;

FIG. 4 represents the same viewed from below.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This apparatus substantially comprises a housing 1 manufactured fromdimensionally stable plastics material, with electric heating means 2arranged inside the housing and a replaceably mounted cylindrical activeingredient carrier 3 of cellulose.

The housing 1 is an assembly composed of a base part 4 in the form of ashell, a middle part 5 arranged above the base 4 and an upper part 6.The parts 4 and 5 have an annular profile and are arranged coaxially andvertically above one another.

The wall of the middle part 5 has the same diameter as the wall of thebase 4, and the upper part 6 is inserted in the middle part 5 to a depthwhich is limited axially and held therein by static friction.

Vent openings 7 in the form of slots are formed in the bottom of thebase 4 and extend to the wall of the base 4.

The rectangular heating means are fixed between the base 4 and middlepart 5 with the broad sides of the heating means 2 extendinghorizontally.

The electric leads 8 to the electric heating means are clamped betweenthe adjacent edges of the housing parts 4 and 5 to relieve tension.Instead of the leads 8, the housing 1 could be equipped with twotransversely extending electric plugs designed to be connected to theelectric heating means 2 (plugs not shown in drawing).

The heating means 2 are fixed in position by means of vertical walls 9extending from the bottom of the base 4 and a frame 10 formed in themiddle part 5.

The said frame 10 is connected to the wall of the middle part 5 bystruts. The cylindrical upper part 6 of the housing is inserted in thecylindrical housing middle part 5 above the frame 10. A coaxial sleeve11 is formed in this upper part 6 and is continuous with the wall of thehousing part 6 through radially extending walls 12.

The exhaust gas duct 13 which is bounded by the wall of the upper part 6and the sleeve 11 is closed at the top by a grating 14 which issufficiently dense to prevent the fingers of the hand being passedthrough it.

Abutments 15 in the form of intersecting transverse rods are provided atthe lower opening of the sleeve 11 to limit the depth of insertion ofthe active ingredient carrier 3.

To facilitate adjustment of the position of the upper part 6 relative tothe middle part 5, the upper part 6 carries two diametrically oppositemanual adjustment devices 16 which can be pushed elastically inwards andfit into parallel vertical slots in the middle part 5 for adjustment ofthe height.

The maximum excursion of the upper part 6 is about 1.5 cm and the sleeve11 with active ingredient carrier 3 is situated at a vertical distanceof about 0.5 cm from the electric heating means.

The active ingredient carrier is inserted with static friction in thesleeve 11 which is closed all round its circumference. When the heatingmeans has reached its operating temperature of about 130° C., itautomatically heats the underside of the active ingredient carrier 3 tosuch a temperature that the active ingredients encapsulated in thecarrier 3 evaporate and are carried upwards by the heated air ascendingthrough the exhaust gas duct 13. The closer the active ingredientcarrier 3 is placed to the electric heating means 2, the more intenselywill the active ingredients be heated and the more rapidly will theyevaporate.

The active ingredient carrier 3 having the dimensions indicated, with adiameter of about 2 cm and an axial length of about 3 cm or more andcontaining about 4.5 g of active ingredient is capable of providing aconstant rate of evaporation of active ingredient over a period of about8 days, during which the carrier 3 should initially be placed at aconsiderable distance from the electric heating means and should then bemoved progressively closer to the heating means as evaporationcontinues.

The rate of outflow of heated air and hence also of evaporated activeingredients may be increased by conically constricting the exhaust gasduct 13 in the upward direction. Instead of or in addition to adjustmentof the height of the active ingredient carrier to alter the degree ofevaporation, heating means with a variable operating temperature may beprovided, but this is not only considerably more expensive than aheating means which has a constant operating temperature but is alsoliable to jeopardize the function of the apparatus if the operatingtemperature rises above 130° C.

It may in some circumstances be advantageous to mount several activeingredient carriers according to the invention above a common heatingmeans.

All novel individual features and combination features disclosed in thedescription and/or drawing are regarded as essential to the invention.

In a preferred embodiment of the apparatus, the cylindrical container 3is provided for receiving the preferably porous active ingredientcarrier and is closed from the heating plate 2 by a base. If thecontainer 3 is made of metal or some other thermally highly conductivematerial, the heat radiated from the heating plate 2 acts on allsections of the wall and base of the container 3 and results inintensive but uniform evaporation of the active ingredients.

According to another embodiment, the sleeve 11 holding the cylindricalcontainer 3 has openings arranged at intervals, i.e. distributed overits circumference, so that the hot air from the heating plate 2 can actthrough these openings on the cylindrical container 3 which is made, forexample, of a thermally highly conductive material, and the container 3is thereby heated substantially uniformly over its whole length orheight. The active ingredients can thereby be evaporated even at lowertemperatures.

What is claimed is:
 1. Apparatus for evaporating active ingredients inan ingredient carrier comprising:a housing defined by first and second,generally tubular, coaxial parts in mutual end-to-end engagement whereinat least a portion of the first part is adapted to fit within the secondpart; the first part including a peripheral wall, a generally axiallyoriented tubular sleeve, having a lower end adjacent the second housingpart, adapted to hold within the sleeve the active ingredient carrier sothat an end face of the carrier is proximate an end of the sleeve, andmeans connecting the sleeve to the peripheral wall to definetherebetween a duct extending from the one end of the first part to theother end thereof; the second part defining a base adapted to supportthe housing on a support surface and including means for flowing air tothe one end of the duct and means operatively engaging the first partpermitting relative axial movements between the parts, the second partfurther including a peripheral wall surrounding the peripheral wall ofthe first part, and including at least one opening through which aportion of the peripheral wall of the first part is exposed, the openingbeing of a sufficient size so that it can be touched with a finger tofacilitate relative axial movement between the first and second parts bytouching the peripheral wall of the first part and forcing it inwardly;and heating means carried by the second part in generally alignment withthe sleeve and situated opposite and generally beneath and the lower endthereof for heating the active ingredient carrier in the tubular sleeve;whereby air heated by the heating means flows through the duct and theend of the first part to the exterior of the housing and the evaporatedactive ingredients released by the carrier are entrained in the airflow; and whereby the rate of active ingredient evaporation can bevaried by changing the relative axial positions of the first and secondparts to correspondingly change the distance between the heating meansand the end face of the carrier in the tubular sleeve.
 2. Apparatusaccording to claim 1, wherein the sleeve and the active ingredientcarrier are placed a chosen vertical distance from the heating means. 3.Apparatus according to claim 1, wherein the sleeve and the activeingredient carrier are placed centrally above the heating means, andwherein the heating means includes a radiant surface which is largerthan the surface area of the carrier end face.
 4. Apparatus according toclaim 1, wherein the sleeve and active ingredient carrier are placedcentrally within the housing.
 5. Apparatus according to claim 1, whereinthe sleeve and the peripheral wall have an annular profile and arearranged coaxially.
 6. Apparatus according to claim 1, wherein thesleeve and the active ingredient carrier are each uniform incross-section over their entire length.
 7. Apparatus according to claim1, wherein the internal cross-section of the first part is greater atthe one end than at the other end.
 8. Apparatus according to claim 1,including a grating covering the duct.
 9. Apparatus according to claim1, including a lid covering the end of the sleeve adjacent the other endof the first part.
 10. Apparatus according to claim 1, includinginwardly projecting abutments at the end of the sleeve proximate the oneend of the first part for limiting the depth of insertion of the activeingredient carrier.
 11. Apparatus for the evaporation of activeingredients in an ingredient carrier comprising:a housing having a basepart, a middle part and an upper part, the base part including a top, aside and a bottom, and at least one ventilation opening, the bottomincluding a generally centrally located support wall extendingvertically upward, the middle part including a top, a side and agenerally centrally located frame disposed in a generally horizontalplane within the middle part, and struts connecting the frame to theside of the middle part, the middle part being coaxially connected tothe top of the base part, and being adapted to receive the upper part,the upper part including a side, a top, a tubular sleeve having exteriorand interior vertical surfaces, radially extending walls connecting thesleeve to the side, the sleeve and the side defining between them anexhaust gas duct, a grating at the top of the upper part permitting thepassage of gases from the duct to the exterior of the housing, thesleeve generally extending over substantially the full length of theupper part and terminating in a sleeve opening which is proximate themiddle part, and abutment rods extending across the sleeve opening,means coaxially positioning and frictionally connecting the upper partto the middle part, and permitting relative axial movement between them;an ingredient carrier adapted to be placed inside the sleeve and havingan end face to engage and be supported by the abutment rods; electricheating means disposed on the frame and supported by the support wall inthe base part so that heat from the heating means rises upwardly towardsthe sleeve and the exhaust gas duct; whereby upon activation, theheating means heats the ingredient carrier to release the activeingredients therein, and the rate of release can be controlled byslidably moving the upper housing part within the middle housing part tovary the spacing between the end face of the ingredient carrier and theheating means.
 12. Apparatus for evaporating active ingredients in aningredient carrier comprising:a housing defined by first and second,generally tubular, coaxial parts in mutual end-to-end engagement whereinat least a portion of the first part is adapted to fit within the secondpart; the first part including a peripheral wall, a generally axiallyoriented tubular sleeve, having a lower end adjacent the second housingpart, adapted to hold within the sleeve the active ingredient carrier sothat an end face of the carrier is proximate an end of the sleeve, thesleeve and active ingredient panel being placed centrally within thehousing and situated centrally above a heating means, and meansconnecting the sleeve to the peripheral wall to define therebetween aduct extending from the one end of the first part to the other endthereof; the second part defining a base adapted to support the housingon a support surface and including means for flowing air to the one endof the duct and means operatively engaging the first part permittingrelative axial movements between the parts, the second part furtherincluding a peripheral wall surrounding the peripheral wall of the firstpart, and including at least one opening through which a portion of theperipheral wall of the first part is exposed, the opening being of asufficient size so that it can be touched with a finger to facilitaterelative axial movement between the first and second parts by touchingthe peripheral wall of the first part and forcing it inwardly; andheating means, including a radiant surface which is larger than thesurface area of the carrier end face, carried by the second part ingenerally alignment with the sleeve and situated opposite and generallybeneath the lower end thereof for heating the active ingredient carrierin the tubular sleeve; whereby air heated by the heating means flowsthrough the duct and the end of the first part to the exterior of thehousing and the evaporated active ingredients released by the carrierare entrained in the air flow; and whereby the rate of active ingredientevaporation can be varied by changing the relative axial positions ofthe first and second parts to correspondingly change the distancebetween the heating means and the end face of the carrier in the tubularsleeve.